The present invention relates to an apparatus and method for cutting an information signal into a metal record carrier. More specifically, it relates to apparatus wherein the angular position of the stylus relative to a surface of the record carrier, and the characteristics of the stylus, associated components and the record carrier are selected and matched to superimpose an oscillation on the information signal which is higher than any frequency in the information signal.
It is known to produce sound or video recordings by cutting information into an original or master record carrier and then to make copies of the master by electrochemical means. Copies having essentially the same quality as the original can be obtained by making copies of the original and then duplicating these copies. However, the cutting of the information signal into the original record carrier must be performed with the utmost precision.
It is customary to cut the information signal into a so-called lacquer foil. Further, U.S. Pat. No. 4,044,379 discloses the use of a metallic record carrier, particularly of copper instead of a lacquer foil, for video recording. An advantage of a copper carrier is that it is substantially harder than a lacquer foil and the resulting quality is better than that obtained from conventional lacquer recordings. U.S. Pat. No. 4,248,488 to Knothe et al also discloses the use of copper as a record carrier wherein the copper has a Vickers hardness of between 110 and 300 kg/mm.sup.2 and the cutting stylus is guided over the metal matrix at a contact angle of between 10.degree. and 20.degree.. The use of these teachings result in video recordings of good quality.
It is not possible to simply transfer this technique to audio record carriers. The known methods are not suitable for audio carriers, which have a much greater groove depth than video recordings, because the resistance exerted against the cutting stylus is substantially greater for audio recordings than for video recordings. Using known techniques, an acceptable surface on the sound groove walls cannot be obtained.
Accordingly, it is an object of the present invention to provide high quality sound recordings made on metallic record carriers as compared to the quality of audio recordings made on lacquer foils.